When attempting to create in a fire zone a breathable, fire extinguishing gas mixture comprising an inert material, carbon dioxide and oxygen, one of the challenges is to ensure that there is an adequate quantity of oxygen in the fire zone in order to sustain mammalian life. When introducing only the inert material and carbon dioxide to the fire zone, there is a possibility that the combustion in the fire zone can consume the free oxygen originally present in the air and, thus, reduce the amount of oxygen in the fire zone below a level sufficient to support life. Accordingly, in accordance with my invention oxygen is included in the gas mixture delivered to the fire zone.
One of the general problems encountered in connection with fighting fires at substantial distances above grade level and using water as the fire extinguishing medium is the weight of the water in the hose or other means for delivering the water to the fire zone. In such situations it is generally not feasible to deliver water much above the seventh or eighth floor of a building. While it has been suggested is to use gaseous materials as the fire extinguishing media, there has been no portable means proposed for the delivery of breathable, fire extinguishing gaseous mixtures comprised of an inert material, carbon dioxide and oxygen to a fire zone.
When considering a portable system for delivering such a mixture to a fire zone several items must be addressed regarding the supply and/or storage of the components of the gas mixture and the admixing of the components of the final fire extinguishing, breathable mixture. Important items to be considered are the temperatures at which the various components are introduced into the system, the temperatures at which the various components liquefy or vaporize, the temperatures at which the various components freeze or solidify and the impact of the temperature of the mixture being delivered. Just as one example, while the temperature of the mixture being delivered to the fire zone can be quite low and not have an adverse impact on the fire extinguishing capability of the mixture, too low a temperature may be undesirable for any people in the fire zone. Additionally, the existence of relatively low temperatures (e.g., below 0° C. or even lower) may require the employment of specific materials in the delivery means. Thus, when very low temperatures are encountered, it becomes undesirable to employ standard fire hoses and other materials of construction must be used, such as, for example, metal conduits. Furthermore, when the temperature of the breathable, fire extinguishing mixture being delivered to the fire zone drops below 0° C. frost begins to form on the delivery means and any water from other hoses splashed onto the delivery means will freeze into ice on the delivery means. This adds additional weight to the delivery means and limits the height to which the delivery means can be lifted. Further, it permits the usual fire hose to remain flexible.
Thus when utilizing liquid nitrogen stored in the portable system of my invention, it is desirable that the liquid nitrogen be vaporized and raised to a temperature greater than the temperature at which carbon dioxide solidifies prior to admixing the vaporized nitrogen and the carbon dioxide. In this type of situation it is also desirable to insure that the temperature is above the freezing point of water (0° C.), thus preventing the formation of ice within the mixture, before having to pump or compress the mixture. Maintaining a temperature at this level will also permit the use of a normal fire hose as the delivery means, rather than heavy metal conduits. Additionally, it is advantageous that the mixture in the delivery means be at a temperature sufficiently high to prevent the formation of frost or ice on the delivery means.
The system of my invention addresses these challenges and provides an improved system for delivering the breathable, fire extinguishing mixture of an inert material, carbon dioxide and oxygen as described herein.
It has previously been suggested to employ various chemicals and mixtures of chemicals, particularly materials in gaseous form in connection with extinguishing fires. For example U.S. Pat. No. 1,926,396 discloses the use of halogen derivatives of hydrocarbons as fire extinguishing materials and suggests that such materials may be pumped from a container or used in pressure devices in which a low boiling compound is employed to create sufficient pressure to expel itself from the apparatus. The patent does not disclose the use of a mixture comprising an inert material, carbon dioxide and oxygen nor does it teach a portable means for dispensing the mixture, which means comprises separate storage vessels for the inert material and carbon dioxide and means for controlling the temperature of the components as they are mixed.
U.S. Pat. No. 2,450,537 describes an apparatus for delivering carbon dioxide to smother a fire by heating the carbon dioxide before introduction into the fire zone, thereby avoiding fogging. There is no mention of a breathable atmosphere much less a system designed to maintain a breathable atmosphere in the fire zone.
U.S. Pat. No. 3,438,445 discloses a system providing a fire fighting gas by burning a fuel and combining the combustion gases with nitrogen and air to produce a mixture of reduced oxygen content, for example about 8% or less. The patent does not recognize the criticality of ensuring a particular concentration of carbon dioxide to create a truly breathable mixture of reduced oxygen content and, thus, provides no apparatus to do so.
U.S. Pat. No. 3,486,562 disclosed an apparatus for detecting and extinguishing a fire in an enclosed environment. When a preselected temperature is reached in the enclosed environment, a heat sensor activates the means for evacuating the gaseous content of the enclosed environment to and accumulator which is at a much lower pressure than the enclosed environment. At the same time, means are provided for cutting off air and power to the enclosed environment, while nitrogen is being introduced to the enclosed environment in place of the evacuated gases.
U.S. Pat. No. 3,715,438 describes a combustion suppressant mixture consisting essentially of certain perfluoroalkane gases and from 16 to 36% oxygen, namely at least about 18% and preferably about 21%. The patent does not disclose or suggest the use of carbon dioxide as a critical component in the mixture and does not describe a portable apparatus for delivering a gaseous mixture.
U.S. Pat. No. 3,822,207 disclosed a fire-fighting composition. Chloropentafluorethane is a general purpose fire extinguishing agent of low toxicity. In a mixture with other halogenatedalkanes, especially bromo-chlorodiflouromethane and bromotriflouromethane, very effective extinguishing compositions may be made giving low concentrations of breakdown products in use against liquid fuel fires.
U.S. Pat. No. 3,840,667 discloses an oxygen-containing atmosphere which will not support combustion but will sustain mammalian life. The oxygen containing atmosphere comprises a mixture of sufficient oxygen to sustain mammalian life; an inert, stable, high heat capacity of polyatomic (perflouroalkane) gas in an amount which provides the oxygen-containing atmosphere with a total heat capacity per mole of oxygen of at least 40 calories per ° C. measured at 25° C. and constant pressure, and helium in an amount of from about 5% to the balance up to 100%. All percentages are in mole %. The atmosphere disclosed in the patent claims to be useful in sustaining mammalian life within any closed system wherein fire hazards would normally be present.
U.S. Pat. No. 3,844,354 also discloses chloropentafluorethane as an efficient and economic fire extinguishing agent for total flooding systems.
U.S. Pat. No. 3,893,514 disclosed a system and method of adding nitrogen under pressure to a confined area including a habitable atmosphere to suppress a fire without any deleterious effect on humans within the environment in which the fire is suppressed. In adding nitrogen to the confined area, the partial pressure of oxygen remains the same to human life, if necessary, whereas the percent by volume oxygen is lowered to a point which is not sufficient to support combustion of burning elements. Therefore, life is sustained while the fire is suppressed with any harmful effect on humans.
U.S. Pat. No. 4,311,198 describes an apparatus for removing smoke from an enclosure by means of a suction-blower unit capable of drawing smoke out of an enclosure or blowing smoke out on an enclosure. The patent also discloses introducing an inert gas, such as nitrogen, into the enclosure to replace the smoke and squelch combustion. The patent does not disclose creating a breathable mixture in the fire zone or the means of so doing.
U.S. Pat. No. 5,327,732 relates to a movable apparatus for storing liquid nitrogen, vaporizing liquid nitrogen and delivering the nitrogen to an oil well fire. There is no discussion of creating or maintaining a breathable atmosphere, particularly not one containing carbon dioxide.
U.S. Pat. No. 5,507,350 describes a method for fire fighting by delivering solid carbon dioxide to or near fire by means of firing capsules of carbon dioxide by means of standard artillery guns. The method apparently works by smothering the fire with carbon dioxide and lowering temperature in the fire area. The patent does not address the question of maintaining a breathable atmosphere in the fire zone. Further, the artillery gun of the patent does not even remotely resemble my system.
U.S. Pat. No. 6,446,731 B1 discloses a self propelled vehicle designed primarily for the removal of smoke from fire zones, but also states that the same apparatus can be used after smoke removal to deliver fire extinguishing materials, such as dry chemicals, water or carbon dioxide, to the fire. The patent does not address the issue of maintaining a breathable atmosphere in a fire zone and does not disclose an apparatus resembling that of the present application.
Thus the suggestions of the prior art do not fully address the creation of a system for the delivery of a breathable, fire extinguishing mixture as defined by my invention.